Research led by Joe Tsien, a neuroscientist at the Medical College of Georgia, did an experiment that showed that something interesting happens with memory as we get older. Their work with mice showed that a part of a receptor on the surface of some neurons that increases with age correlated with more difficulty in forming long term memories. The mice with these adult levels of NR2A also struggled to weaken their synapses, which is essential for forgetting some information to remember new useful data.
So what can you really do about a memory you no longer want? There are two main things:
1) Direct Suppression which means trying to block out any thoughts you have around this particular memory
2) Thought Substitution which means trying to substitute the undesired memory with more desired one.
For interest: The first strategy increases activity in the prefrontal cortex (right dorsolateral area to be precise) and reduces activity in the hippocampus (important for conscious recollection). The second increases activity again in the prefrontal cortex, but this time the left caudal area and also the midventrolateral area.
Practically what does this mean? It is useful to know that there is a process to forming memories of things and this process seems to get less efficient in a way as we get older. (Children find it easier to learn new languages for example). However by approaching new learning in a strategic way, being committed to putting in effort and getting some good learning techniques in place (not just relying on old ones that you’ve used in the past) you set yourself up best for success.